Sad Lamp Exposure Of Pcb?

[bitem2k]

Hi,
Does anyone know if SAD lamps emit enough UV to expose photo pcbs?

I came across link (**broken link removed**), which describes using flourescent lights.

I own one of these (**broken link removed**) sad lamps allready, and would like to use this if possible to expose pcbs.

thanks very much

 

[Oznog]

PCBs require UV light. Normal flourescent tubes do not emit significant UV. Blacklight tubes, tanning lights, and some exotic types of white flourescent tubes do. You can get BL tubes at the hardware store usually.

I doubt the SAD lamps have the necessary UV. Well, they might, but probably not because UV is generally regarded as dangerous and expose them to liability.

 

[3v0]

I agree with Oznog.

But you could do a test. Lay out a dense pattern or a grid. Then expose the board. Start with the most of the board covered with dense cardboard or foil. After your suspected min exposure time uncover a bit more of the board every minute or so. You will end up with strips of the board exposed for min, min+1, min+2 etc.

Develop the board to see what time worked best.

3v0

 

[Hero999]

Hi,
Does anyone know if SAD lamps emit enough UV to expose photo pcbs?

I don't know, it depends on the wavelength of UV light they emit, you need UVA light for developing PCBs.

I came across link (**broken link removed**), which describes using flourescent lights.

No, that project uses germicidal tubes they aren't fluorescents but low pressure mercury discharge lamps without the fluorescent coating; they're made of quartz to pass the 253.7nm shortwave UV radiation.

Do not use germicidal tubes, use blacklight or incest killer tubes. Apart from being very dangerous, it's the wrong wavelength for developing PCBs, you need UVA radiation between 350nm to 380nm to develop PCBs, 253.7nm is useless.

By all means build this project but subsitute the G15T8 tubes for BLB15T8 or BL15T8 tubes.

I have seen this project before on that website and have politely emailed them asking them to rectify it but they haven't.

I own one of these (**broken link removed**) sad lamps allready, and would like to use this if possible to expose pcbs.

I don't know, it depends on the type of UV it outputs, UVA is fine but don't bother if it's UVB, by all means try it but you're probably better of with insect killer tubes which are cheaper too.

 

[bitem2k]

Nice one everyone,
The reason i want to use this sad lamp is that im ultra skint at the mo, after purchasing loads of electronic bits and pieces.

I dont hold out much hope for it working, but as suggested i will give it a bash on a small piece.

thanks again.

 

[justDIY]

or buy the kind of pcb's that don't require uv light

I don't know where in the world you're from, but here in the States, most of the photo boards are pretty broad band, working with normal incandescent all the way through to shortwave UV - the only thing you change is the exposure time. ~8 min for fluorescent or ~90 sec for shortwave UV

 

[Hero999]

working with normal incandescent all the way through to shortwave UV - the only thing you change is the exposure time. ~8 min for fluorescent or ~90 sec for shortwave UV

The problem with shortwave UV is it's often blocked by the plastic film or tracing paper (upon which the artwork is printed) and the glass in the exposure box.

I haven't tried incandescent lamps but I've heard that they take ages to expose a board.

 

[justDIY]

I think the emulsion relies more on the visible blue/violet component of a UV lamp, rather than the invisible ultraviolet rays themselves.

 

[Hero999]

That's probably true to some extent, have you ever tried an incandescent lamp?

 

[justDIY]

yes, I used a 100 watt soft white incandescent, as recommended in the instructions, suspended high above the board. I recall exposing for roughly 20min.

I now use a pair of 15w fluorescent tubes, placed very near the board, and I expose 8-9 min.

 

[bitem2k]

thanks very much.

 

[bitem2k]

Hi, the Sad Lamp appears to work. but it takes about 15min.

thanks

 

[justDIY]

sounds about right ... your SAD lamp is probably similar to my fluorescents, in that it's emulating daylight (I use 6500k daylight tubes)

whats the hurry anyway?

 

[bitem2k]

Definately i agree with you, no rush!

 

[Hero999]

If you really want to save time then use insect killer tubes like I said before.

 

[bitem2k]

when i start producing more pcbs i will probably invest.

thanks